In this study, the existence of cells bearing interleukin-2 (IL-2) or IL-2 receptors in the normal and the 1-methyl-4-phenyl-pyridinium (MPP+)-lesione brain of rats has been investigated. Autoradiography showed that radiolabeled-IL-2 did not bind to the cryo-sliced normal brain sections. While intrastriatal administration of MPP+ caused visible damage in the vicinity of the injected region two weeks after injection, the radiolabeled IL-2 did not react with the lesioned site. Addition of anti-IL-2 antibodies plus trace amounts of radiolabeled IL-2, on the other hand, elicited a selective radiolabeling of cells localized at the MPP+-lesioned region. Thi autoradiographic imaging result indicates the accumulation of cells bearing IL-2-like molecules at the HPP+induced lesion site. The finding may provide clues to the understanding of the distribution and function of IL-2 in the degenerated central nervous system. RNA extracted from both normal and lesioned brains followed by probing with IL2, however, showed no difference suggesting that the accumulation of IL-2-like molecules is not due to synthesis of IL-2 molecules.